1. Field of the Invention
This invention relates, generally, to sheet feeders of the stand-alone type or of the type used in conjunction with other sheet feeders or as a part of other machines. More particularly, it relates to a sheet feeder capable of handling sheets of widely varying thickness.
2. Description of the Prior Art
There are many different types of sheet feeders and there are hundreds of uses for them. Typically, high speed sheet feeders are used when it is desired to insert sheets of paper or other flat items into envelopes, containers, bins or the like in large quantities and in short periods of time.
The primary parts of a sheet feeder include a bin for holding a stack or nearly vertical stack of sheets of paper or similar thin, flat items, a wedge-shaped support member at the bottom of the sheet feeder that tilts the stack of sheets from a vertical plane, a separator wheel near the bottom of the sheet feeder, a guide plate mounted adjacent to the separator wheel, and a conveyor belt at the bottom of the sheet feeder that transports sheets away from the sheet feeder as they are dispensed. A nip area is defined as an area between the lowermost point of the separator wheel and the conveyor belt. Each sheet of paper dispensed by the sheet feeder must pass through the nip area, one at a time, so that the lowermost sheets, as they are sequentially pulled from the bottom of the stack, are shingled when they are transported away from the feeder by the conveyor belt. The wedge-shaped support member biases the sheets toward the nip area.
U.S. Pat. No. 3,908,983 (1974) discloses a separator wheel, also known as a gate means, having a diameter of about one and one-quarter inches. Thus, its radius is about five-eighths of an inch. A straight guide plate is mounted between the separator wheel and the stack of paper in the sheet feeder bin; the guide plate is of smooth, metallic construction so that it presents a low friction surface so that paper slides easily relative to it. If the edges of the sheets of paper were to rub against the separator wheel as they approached the nip, they could get hung up on the relatively high friction surface presented by the separator wheel and thus fail to enter into the nip area.
If relatively thick items, such as audiocassettes, are to be inserted into containers or envelopes at high speeds, the separator wheel and guide plate just described cannot be used. That assembly has utility only in connection with relatively thin sheets because a large plurality of thin sheets can curve around the perimeter of the wheel and be constrained to enter into the staggered configuration as described above. However, if a stack of audio cassette tapes, each a quarter of an inch thick, is fed into a sheet feeder, the curvature of the small separator wheel presents a profile to the cassettes that is similar to the profile of a vertical flat wall; the machine thus cannot be used to dispense such thick items into containers or envelopes.
The obvious solution to this problem is to design different machines for high speed dispensing of thick articles into containers or envelopes; that is what the industry has been doing for the past twenty five years. Most of the machines that have been developed eschew the guide plate and the separator wheel/gate means and employ vacuum-reliant means and various other means for high-speed insertion of thick articles into envelopes. Those machines that retain the gate means concept simply increase the size of the nip area by adjusting the position of the gate means so that thicker sheets can run through the feeder. This patch applied to the problem is inadequate, however, and such machines jam at an unacceptable rate.
The machines that have been developed to handle the high speed feeding of thick articles without relying on a gate means have the opposite problem of the gate meansreliant machines; they do not handle thin articles well.
Moreover, they are of complex mechanical construction and thus are not inexpensive.
Those businesses having both thick and thin articles that require high speed dispensing of sheets or other articles into bins, containers, envelopes, or the like must purchase at least a first machine having a conventional small diameter separator wheel and a straight guide plate means for handling thin sheets and at least a second machine of different design for handling thick sheets or other thick articles.
There is a clear need for a high-speed sheet feeder capable of dispensing flat articles of widely differing thickness. This would enable many customers to purchase one machine for all their needs.
Scores if not hundreds of skilled machine designers have endeavored for the past quarter century to overcome the limitations of the known sheet feeders. The only successful attempts at overcoming the shortcomings, however, have resulted in entirely re-designed machines having no gate means whatsoever, as mentioned above.
Clearly, then, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how the limitations of gate means-reliant machines could be overcome in a way that would not require the invention of an entirely different machine.
The long-standing but heretofore unfulfilled need for an innovation that overcomes the limitations of the prior art is now met by a new, useful, and nonobvious invention.
The present invention is an improved sheet feeder for high speed dispensing of sheets of widely varying thickness into containers, envelopes or the like.
It includes a bin means for holding a plurality of sheets in a substantially vertical array and means for dispensing sheets in sequence from the bottom of the bin.
A novel gate means or separator wheel having a diameter of about three inches is positioned at the discharge end of the sheet feeder. A metallic shroud is positioned between the sheets in the bin and the separator wheel to provide a low friction surface to the sheets so that they do not become bound as they travel downwardly in the bin.
More particularly, the shroud has a first straight part, a curved part that conforms to a contour of the separator wheel and a second straight part disposed at a substantially ninety degree angle to the first straight part. The second straight part is disposed in parallel, predetermined spaced apart relation to a conveyor belt means that transports sheets from the sheet feeder.
The first straight part provides a smooth, low friction surface so that sheets traveling downwardly in the bin means as sheets are sequentially dispensed from a lowermost end of the bin means slide easily against the first straight part. The curved part of the shroud serves to shingle the sheets as they approach the nip area, thereby breaking frictional bonds that may have been holding contiguous sheets together. The second straight part of the shroud is slotted so that sheets entering into the nip area are contacted by the separator wheel, said separator wheel having a higher coefficient of friction relative to said sheets than said shroud member.
A wedge-shaped support means at the lowermost end of the bin biases the lowermost sheets in the stack toward the nip area.
It is a primary object of this invention to advance the art of sheet feeders by providing a sheet feeder capable of dispensing flat objects of widely varying thickness.
Another object is to provide such a machine in the absence of completely re-designing the machines heretofore capable of handling thin sheets and incapable of handling thick sheets.
These and other important objects, features, and advantages of the invention will become apparent as this description proceeds.
The invention accordingly comprises the features of construction, combination of elements and arrangement of parts that will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.